In this paper we perform large eddy simulations of variable density mixing layers, which originate from initially laminar conditions. The aim of this work is to capture the salient flow physics present in the laboratory flow. This is achieved through varying the nature of the inflow condition, and assessing the vortex structure present in the flow. Two distinct inflow condition types are studied; the first is an idealised case obtained from a mean inflow velocity profile with superimposed pseudo-white-noise, and the second is obtained from an inflow generation technique. The inflow conditions generated have matching mean and root mean squared statistics. Validation of the simulations is achieved through grid dependency and subgrid-scale model testing. Regardless of the inflow condition type used, the change in growth rate of the mixing layer caused by the density ratio is captured. It is found that the spacing of the large-scale spanwise structure is a function of the density ratio of the flow. Detailed interrogation of the simulations shows that the streamwise vortex structure present in the mixing layer depends on the nature of the imposed inflow condition. Where white-noise fluctuations provide the inflow disturbances, a spatially-stationary streamwise structure is absent. Where the inflow generator is used, a spatially stationary streamwise structure is present, which appears as streaks in plan-view visualisations. The stationary streamwise structure evolves such that the ratio of streamwise structure wavelength to local vorticity thickness asymptotes to unity, independent of the density ratio. This value is in agreement with previous experimental studies. Recommendations are made on the requirements of inflow condition modelling for accurate mixing layer simulations.

在本文中，我们对源自最初层流条件的可变密度混合层进行大涡模拟。这项工作的目的是捕捉实验室流动中存在的突出流动物理。这是通过改变流入条件的性质和评估流动中存在的涡流结构来实现的。研究了两种不同的流入条件类型；第一个是从具有叠加伪白噪声的平均流入速度剖面获得的理想情况，第二个是从流入生成技术获得的。生成的流入条件具有匹配的均值和均方根统计量。模拟的验证是通过网格依赖性和亚网格尺度模型测试来实现的。无论使用何种流入条件类型，捕获由密度比引起的混合层生长速率的变化。发现大尺度展向结构的间距是流动密度比的函数。对模拟的详细询问表明，混合层中存在的流向涡结构取决于所施加的流入条件的性质。在白噪声波动提供流入扰动的情况下，不存在空间静止的流向结构。在使用流入发生器的地方，存在空间静止的流向结构，在平面视图中显示为条纹。静止流向结构演变为流向结构波长与局部涡度厚度之比渐近统一，与密度比无关。该值与先前的实验研究一致。针对准确混合层模拟的流入条件建模要求提出了建议。